Methods for manufacturing components from articles formed by additive-manufacturing processes

ABSTRACT

A method is provided for manufacturing a component. The method includes forming a diffusion coating on a first intermediate article formed by an additive manufacturing process. The diffusion coating is removed from the first intermediate article forming a second intermediate article. The diffusion coating is formed by applying a layer of coating material on at least one surface of the first intermediate article and diffusion heat treating the first intermediate article and the layer. The diffusion coating comprises a surface additive layer and a diffusion layer below the surface additive layer. The formation of the diffusion coating and removal thereof may be repeated at least once.

PRIORITY CLAIM

This application is a continuation of U.S. application Ser. No.13/235,210, filed Sep. 16, 2011.

TECHNICAL FIELD

The present invention generally relates to methods for manufacturingcomponents, and more particularly relates to methods for manufacturingcomponents from articles formed by additive-manufacturing processes.

BACKGROUND

Components with relatively complex three-dimensional (3D) geometriesraise difficult fabrication issues. Conventional fabrication techniquesinclude forging, casting, and/or machining. Such conventional methodsare not only expensive and have long lead-times, but may additionallyhave low yields. Development time and cost for certain components mayalso be magnified because such components generally require severaliterations, including iterations as a result of intentional designdecisions.

Additive manufacturing (AM) processes (including those which form“cores” for subsequent conventional casting) have been developed tofabricate components having relatively complex three dimensionalgeometries, including components with internal surfaces defininginternal passages including internal hollow areas, internal channels,internal openings or the like (collectively referred to herein as“internal passages”) for cooling, weight reduction, or otherwise.Additive Manufacturing (AM) is defined by the American Society forTesting and Materials (ASTM) as the “process of joining materials tomake objects from 3D model data, usually layer upon layer, as opposed tosubtractive manufacturing methodologies, such as traditional machiningand casting.” In an additive-manufacturing process, a model, such as adesign model, of the component may be defined in any suitable manner.For example, the model may be designed with computer aided design (CAD)software. The model may include 3D numeric coordinates of the entireconfiguration of the component including both external and internalsurfaces. The model may include a number of successive 2Dcross-sectional slices that together form the 3D component.

Components manufactured from additive manufacturing processes may havesignificant surface roughness, surface porosity and cracks (hereinafter“surface-connected defects”), and internal porosity and cracks(hereinafter “internal defects”). The term “internal defects” alsoincludes bond failures and cracks at the interfaces between successivecross-sectional deposit layers. Cracks may develop at these interfacesor cut through or across deposit layers dues to stresses inherent withthe additive manufacturing process and/or the metallurgy of the buildmaterial.

A hot isostatic pressing (HIP) process may be used to eliminate internaldefects but not the surface-connected defects. For components needingHIP because of the presence of internal defects, an encapsulationprocess may be used to bridge and cover the surface-connected defects,effectively converting the surface-connected defects into internaldefects in preparation for subsequent hot isostatic pressing (HIP)processing. However, for components with significant surface roughness,the encapsulation process may not sufficiently bridge and cover thesurface-connected defects. Surface roughness may also be objectionableto customer perception of quality and may interfere with thefunctionality of the component. For example, excessive surface roughnessmay restrict or impede airflow, collect debris, act as a stress riser,and otherwise detract from the component design.

Unfortunately, the reduction of internal passage surface roughnesspresents a particular manufacturing challenge because of the generalinaccessibility of the internal passage surfaces. Conventional polishingor milling techniques to reduce internal passage surface roughness arenot as developed as they are for external surfaces. No effective processexists to uniformly reduce internal passage surface roughness toacceptable levels, thereby compromising the structural integrity,cosmetic appearance, functionality, and mechanical properties of thecomponent, and also not allowing the encapsulation process tosufficiently bridge and cover the surface-connected defects inpreparation for HIP processing. Even with encapsulation, faying surfacesof some surface-connected defects may not be sufficientlymetallurgically diffusion bonded if excessively oxidized or otherwiseinsufficiently cleaned. A component with inadequate diffusion bondedsurfaces has a compromised metallurgical surface integrity that reducesthe overall metallurgical quality of the manufactured component.

Accordingly, it is desirable to provide methods for manufacturingcomponents from articles formed by additive-manufacturing processes. Itis also desirable to provide methods that uniformly reduce surfaceroughness, including internal passage surface roughness, therebyimproving the structural integrity, cosmetic appearance, functionality,mechanical properties, and fatigue life/strength of the component, thatallow encapsulation of the additive-manufactured article to be effectivein preparation for subsequent hot isostatic pressing (HIP) processing,and that improve metallurgical quality of the component. It is alsodesirable to provide methods for manufacturing components that improveyield, enable improved development cycle times and reduced tooling costswithout sacrificing component performance or durability, enable multipledesign iterations at relatively low cost and short delivery times, andpermit internal configurations for components not otherwise possiblewith current casting technology. Furthermore, other desirable featuresand characteristics of the present invention will become apparent fromthe subsequent detailed description of the invention and the appendedclaims, taken in conjunction with the accompanying drawings and thisbackground of the invention.

BRIEF SUMMARY

Methods are provided for manufacturing a component. In accordance withone exemplary embodiment, the method comprises forming a diffusioncoating on a first intermediate article formed by an additivemanufacturing process. The diffusion coating is removed from the firstintermediate article forming a second intermediate article having atleast one enhanced surface.

Methods are provided for manufacturing a component from a firstintermediate article formed by an additive manufacturing process inaccordance with yet another exemplary embodiment of the presentinvention. The method comprises applying a coating material layer on asurface of the first intermediate article. The first intermediatearticle and the coating material layer are diffusion heat treated toform a diffusion coating comprising a surface additive layer and adiffusion layer below the surface additive layer. The diffusion layerincludes an upper portion of a substrate of the first intermediatearticle. The diffusion coating including the upper portion of thesubstrate from the first intermediate article is removed forming asecond intermediate article. The applying, diffusion heat treating, andremoving steps are optionally repeated at least once.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will hereinafter be described in conjunction withthe following drawing figures, wherein like numerals denote likeelements, and

FIG. 1 is a partial cross-sectional view of a turbine section of anexemplary gas turbine engine assembly;

FIG. 2 is an isometric view of an exemplary turbine component;

FIG. 3 is a flowchart of a method for manufacturing a component (such asthe exemplary turbine component of FIG. 2) from a first intermediatearticle, according to exemplary embodiments of the present invention;

FIG. 4 is an exemplary system for forming an exemplary firstintermediate turbine article;

FIG. 5 is a cross-sectional view of an exemplary first intermediateturbine article including a substrate and having a plurality of internalpassages, the first intermediate turbine article having internal andsurface-connected defects, with a polished external surface and roughinternal passage surfaces;

FIG. 6 is a cross-sectional representation of a portion of the substrateof the exemplary first intermediate turbine article of FIG. 5, furtherillustrating an internal defect and a representative rough internalpassage surface having surface-connected defects;

FIG. 7 is a cross-sectional representation similar to FIG. 6 in themethod of FIG. 3 in accordance with exemplary embodiments, illustratinga coating material layer on the rough internal passage surface of FIG.6;

FIG. 8 is a cross-sectional representation similar to FIGS. 6 and 7 inthe method of FIG. 3 in accordance with exemplary embodiments,illustrating the coating material layer after diffusion thereof to forma diffusion coating on the representative rough internal passage surfaceof FIGS. 6 and 7, the diffusion coating including an upper portion ofthe substrate above a diffusion coating boundary and comprising asurface additive layer and a diffusion layer below the surface additivelayer, the surface additive layer and/or the diffusion layer alsoserving as an encapsulation layer, making subsequent encapsulation in afinishing step unnecessary;

FIG. 9 is a cross-sectional representation similar to FIGS. 6 through 8in the method of FIG. 3 in accordance with exemplary embodiments afterremoval of the diffusion coating from the representative rough internalpassage surface of the first intermediate article, the diffusion coatingboundary forming an enhanced surface on a second intermediate turbinearticle (shown in FIG. 10), the enhanced surface having reduced surfaceroughness, the residual surface-connected cracks below the diffusioncoating boundary having diffusion bond failures;

FIG. 10 is a cross-sectional view of a second intermediate turbinearticle with reduced surface roughness;

FIG. 11 is a cross-sectional view of the second intermediate turbinearticle of FIG. 10 after encapsulation in a finishing step to form anencapsulated article, in the method of FIG. 3 in accordance withexemplary embodiments;

FIG. 12 is a cross-sectional view of a consolidated turbine articleafter HIP processing of the encapsulated article of FIG. 11 to reduce oreliminate the internal defects in the method of FIG. 3 in accordancewith exemplary embodiments;

FIG. 13 is a cross-sectional view of a finished turbine component in themethod of FIG. 3 after removal of the encapsulation layer from theconsolidated turbine article of FIG. 12 in accordance with exemplaryembodiments;

FIG. 14 is an image of an exemplary as-built high pressure (HP) turbineblade (an exemplary first intermediate article) formed from a DMLSadditive manufacturing process, illustrating a rough internal passagesurface and a rough external surface;

FIG. 15 is an image of the as-built HP turbine blade of FIG. 14 afterencapsulating and HIP processing of a polished external surface andrough internal passage surfaces, illustrating residual internal surfaceroughness and surface-connected defects;

FIG. 16 is an image of a representative internal passage surface of theas-built HP turbine blade of FIG. 15, illustrating in more detailresidual internal passage surface roughness and surface-connecteddefects; and

FIG. 17 is an image of the internal passage surface of FIG. 16 afterformation of an aluminide diffusion coating thereon but prior to coatingremoval, illustrating a coating diffusion boundary adapted to define anenhanced inner passage surface after subsequent removal of the aluminidediffusion coating.

DETAILED DESCRIPTION

The following detailed description is merely exemplary in nature and isnot intended to limit the invention or the application and uses of theinvention. As used herein, the word “exemplary” means “serving as anexample, instance, or illustration.” Thus, any embodiment describedherein as “exemplary” is not necessarily to be construed as preferred oradvantageous over other embodiments. All of the embodiments describedherein are exemplary embodiments provided to enable persons skilled inthe art to make or use the invention and not to limit the scope of theinvention which is defined by the claims. Furthermore, there is nointention to be bound by any expressed or implied theory presented inthe preceding technical field, background, brief summary, or thefollowing detailed description.

Various embodiments are directed to methods for manufacturing componentsfrom articles formed by an additive manufacturing process such aselectron beam melting or direct metal laser fusion in which sequentialdeposit layers of build material are fused and solidified according to athree-dimensional (3D) model. Other additive manufacturing processes mayalso be employed. The as-built article (hereinafter referred to as a“first intermediate article”) may have significant surface roughnesscaused, for example, by partial fusion or entrainment of metallic powderas the laser starts or stops its traverse or sweep at the edges of theeach deposit layer, and by contamination, debris, oxidation, or thelike. The first intermediate article may also have internal porosity andcracks (hereinafter “internal defects”) and surface porosity and cracks(hereinafter “surface-connected defects”). The term “internal defects”also includes “interface defects” such as bond failures and cracks atthe interfaces between successive cross-sectional layers. The cracksdevelop at these interfaces or cut through or across deposit layers dueto stresses inherent with the additive manufacturing process and/or themetallurgy of the build material. The term “surface-connected defects”as used herein includes porosity or cracks that are connected to thesurface of the component. The surface-connected cracks have fayingsurfaces that may not be adequately metallurgically diffusion bonded. Asused herein, the term “surface roughness” includes roughness at thesurface (the intended sharp edge of the first intermediate article),near surface (the roughness associated with loosely adhered particles),and subsurface (the surface-connected defects contributing toroughness). The reduction in surface roughness improves the structuralintegrity, cosmetic appearance, functionality, fatigue life/strength,and mechanical properties of the component. Unfortunately, reduction ofinternal passage surface roughness presents a particular additivemanufacturing challenge because of the general inaccessibility of theinternal passage surfaces. As used herein, the term “internal passage”includes an internal hollow area, an internal channel, an internalopening or the like. According to exemplary embodiments as describedherein, in a method for manufacturing a component, a diffusion coatingis formed on the first intermediate article. The diffusion coating isformed by applying a layer of coating material (hereinafter “coatingmaterial layer”) on a surface of the first intermediate article anddiffusion heat treating the first intermediate article and the layer.The diffusion coating (including what remains of the coating materiallayer) is removed from the first intermediate article forming a secondintermediate article having an enhanced surface. Formation and removalof the diffusion coating may be repeated at least once. As used herein,the term “enhanced” or the like refers to a reduction in surfaceroughness and/or improvement in metallurgical quality and the term“enhanced surface” includes an enhanced surface, near surface, andsubsurface. The improvement in metallurgical quality results fromremoving surfaces that include surface-connected defects havinginadequately metallurgically diffusion bonded faying surfaces. In anembodiment, the applied and diffused coating material layer also servesas an encapsulation layer to bridge and cover the surface-connecteddefects to effectively convert the surface-connected defects intointernal defects that may be reduced or substantially eliminated by ahot isostatic pressing (HIP) process or other consolidation treatment,as hereinafter described. In another embodiment, the second intermediatearticle may be encapsulated by an encapsulation layer in a finishingstep. In various embodiments, the HIP process may be concurrentlyperformed with the diffusion heat treating step, subsequently performedin a finishing step, and at other times. These manufacturing methodsyield a component with improved structural integrity, cosmeticappearance, functionality, metallurgical quality, and overall mechanicalproperties, including improved tensile and stress rupture strengths,improved fatigue life/strength, and improved manufacturing yield, enableimproved development cycle times, reduce tooling costs withoutsacrificing component performance or durability, and permit internalconfigurations for components not otherwise possible with conventionalfabrication techniques.

While the advantages of the present invention as described herein willbe described with reference to a turbine component (a high pressureturbine blade shown in FIGS. 2, 4-5, and 10-17), the teachings of thepresent invention are generally applicable to any component manufacturedfrom a first intermediate article formed by an additive manufacturingprocess and may be used to reduce surface roughness and/or improvemetallurgical quality of the manufactured component. The teachings ofthe present invention are especially applicable to componentsmanufactured from a first intermediate article formed by an additivemanufacturing process, and that may include internal passages withrelatively inaccessible rough internal surfaces (hereinafter “internalpassage surfaces”). Exemplary components include, but are not limitedto, turbine components, medical devices, weapons, and custom low volumecomponents for internal combustion racing engines, etc.

FIG. 1 is a fragmented vertical sectional view illustrating a partialturbine section 100 of a gas turbine engine assembly in accordance withan exemplary embodiment. The turbine section 100 and gas turbine engineassembly have an overall construction and operation that is generallyunderstood by persons skilled in the art. In general terms, the turbinesection 100 has a housing 102 with an annular duct wall 104 that definesa mainstream hot gas flow path 106 for receiving a flow of mainstreamcombustion gases 108 from an engine combustor (not shown). The housing102 additionally houses at least one stator assembly 110 with statorvanes 120 and at least one turbine rotor assembly 130 with turbine rotorblades 132. The rotor blades 132 of the turbine rotor assembly 130project radially outward from a turbine rotor platform 134 that iscoupled to a turbine disk 136, which in turn circumscribes a shaft (notshown). During operation, the combustion gases 108 flow past axiallyspaced circumferential rows of stator vanes 120 and rotor blades 132 todrive the rotor blades 132 and the associated turbine rotor assembly 130for power extraction. Other embodiments may be differently arranged.

FIG. 2 is an isometric view of a turbine component 200 in accordancewith an exemplary embodiment and generally illustrates the relativelycomplex 3D geometric configuration typical of a turbine component, forexample that may be incorporated into the turbine section 100 of FIG. 1.Although the turbine component 200 in FIG. 2 is depicted as a rotorblade, such as rotor blade 132 (FIG. 1), the exemplary embodimentsdiscussed herein are applicable to any type of turbine component, suchas stator vanes 120 (FIG. 1), and other engine components such as fancomponents, compressor components, and combustion components, as well asother components as noted above.

The turbine component 200 may include an airfoil 202 with a generallyconcave pressure side 204 and a generally convex suction side 206opposed thereto. Each airfoil 202 may be coupled to a platform 210 thatdefines an inner boundary for the hot combustion gases that pass overairfoil 202 during engine operation. A mounting dovetail 212 may beintegrally formed on the underside of the platform 210 for mounting theturbine component 200 within the turbine section 100 (FIG. 1). In anexemplary embodiment, the turbine component may include internalpassages 502 (FIG. 5) to provide a cooling flow during engine operation.In this exemplary embodiment, the turbine component (FIG. 13) has aplurality of internal passages each with an internal surface 304 a, andan external surface 304 b. In other embodiments, the turbine componentmay be solid with only an external surface 304 b.

As shown in FIGS. 2 through 5, in accordance with exemplary embodiments,a method 10 for manufacturing a component, such as the turbine component200 of FIG. 2, begins by providing a first intermediate article 500formed by an additive manufacturing process (step 300) (FIG. 3). Thefirst intermediate article 500 may be a first intermediate turbinearticle adapted to be formed into the turbine component 200. The method10 includes a number of intermediate stages during manufacture of thecomponent, illustrated in the cross-sectional views of FIGS. 7-11, priorto completion of the finished component, illustrated in FIG. 2 and thecross-sectional view of FIG. 12.

As noted above, Additive Manufacturing (AM) is defined by the AmericanSociety for Testing and Materials (ASTM) as the “process of joiningmaterials to make objects from 3D model data, usually deposit layer upondeposit layer, as opposed to subtractive manufacturing methodologies,such as traditional machining and casting.” In an additive-manufacturingprocess, a model, such as a design model, of the component may bedefined in any suitable manner. For example, the model may be designedwith computer aided design (CAD) software. The model may include 3Dnumeric coordinates of the entire configuration of the componentincluding both external and internal surfaces of an airfoil, platformand dovetail. The model may include a number of successive 2Dcross-sectional slices that together form the 3D component.

Some examples of additive manufacturing processes include: micro-pendeposition in which liquid media is dispensed with precision at the pentip and then cured; selective laser sintering in which a laser is usedto sinter a powder media in precisely controlled locations; laser wiredeposition in which a wire feedstock is melted by a laser and thendeposited and solidified in precise locations to build the product;electron beam melting; laser engineered net shaping; and direct metaldeposition. In general, additive manufacturing techniques provideflexibility in free-form fabrication without geometric constraints, fastmaterial processing time, and innovative joining techniques. In oneexemplary embodiment, direct metal laser fusion (DMLF) is used toproduce the additive-manufactured article. DMLF is a commerciallyavailable laser-based rapid prototyping and tooling process by whichcomplex parts may be directly produced by precision melting andsolidification of metal powder into successive deposit layers of largerstructures, each deposit layer corresponding to a cross-sectionaldeposit layer of the 3D component. DMLF may include direct metal lasersintering (DMLS). Direct Metal Laser Sintering (DMLS) is an additivemanufacturing process that fuses powder metal in progressive depositlayers. With DMLS, the fused sintered powder contains more porosity thanDMLF, which in turn may necessitate a HIP process for densification.Other differences may include speed of building the first intermediatearticle, grain or deposit size, etc.

FIG. 4 illustrates an exemplary system 400 for forming the firstintermediate article 500 described above and provided in step 300 ofmethod 10. As noted above, the first intermediate article 500 may be thefirst intermediate turbine article as shown in FIG. 5. As noted above,the system 400 may be an additive manufacturing system such as a DMLSsystem that includes a fabrication device 410, a powder delivery device430, a scanner 440, and a laser 460 and functions to produce the firstintermediate turbine article 500 from build material 470.

The fabrication device 410 includes a build container 412 with afabrication support 414 carrying the first intermediate turbine article500 to be formed from the build material 470. The fabrication support414 is movable within the build container 412 in a vertical directionand is adjusted in such a way to define a working plane 416. Thedelivery device 430 includes a powder chamber 432 with a deliverysupport 434 that supports the build material 470 and is also movable ina vertical direction. The delivery device 430 further includes a rolleror wiper 436 that transfers build material 470 from the delivery device430 to the fabrication device 410.

During operation, the fabrication support 414 is lowered and thedelivery support 434 is raised. The roller or wiper 436 scraps orotherwise pushes a portion of the build material 470 from the deliverydevice 430 to form the working plane 416 in the fabrication device 410.The laser 460 emits a laser beam 462, which is directed by the scanner440 onto the build material 470 in the working plane 416 to selectivelyfuse the build material 470 into a cross-sectional deposit layer of thefirst intermediate turbine article 500. More specifically, the laserbeam 462 selectively fuses the powder of the build material 470 intolarger structures by rapidly melting the powder particles. As thescanned laser beam 462 moves on, heat is conducted away from thepreviously melted area, thereby leading to rapid cooling andresolidification. As such, based on the control of the laser beam 462,each deposit layer of build material 470 will include unsintered buildmaterial 470 and sintered build material that forms the cross-sectionaldeposit layer of the first intermediate turbine article 500. Anysuitable laser and laser parameters may be used, includingconsiderations with respect to power, laser beam spot size, and scanningvelocity.

The first intermediate article may be manufactured from a build material470 comprising a superalloy such as a nickel-based superalloy or acobalt-based superalloy, as well as high temperature stainless steels,titanium, chromium, or other alloys, or a combination thereof. Exemplaryhigh temperature, high strength DMLS polycrystalline alloys include ahigh temperature nickel base superalloy such as MAR-M-247 (also known asMM 247) and IN 718 or IN 738 available (in powder form) from, forexample, Allegheny Technologies Incorporated (ATI), Pittsburgh, Pa.Notable substrate materials (for epitaxial deposits) includedirectionally-solidified (DS) alloys such as DS CM247 LC andsingle-crystal (SX) alloys such as CMSX-486 available (in ingot form)from, for example, the Cannon Muskegon Corporation, Muskegon, Mich.Epitaxial deposits involve fusing the powder and remelting theunderlying build material such that during solidification, the deposittakes on the crystallographic orientation of the substrate, ideally adirectional solidified polycrystalline or single crystal structure.Nickel and cobalt-based superalloys are most often used to fabricate gasturbine components because of the high strength required for longperiods of service at the high temperatures characteristic of turbineoperation. The powder build material 470 may be selected for enhancedstrength, durability, and useful life, particularly at hightemperatures. Each successive deposit layer of the first intermediatearticle may be, for example, between 10 μm and 200 μm, although thethickness may be selected based on any number of parameters. It is to beunderstood that for other components not subjected to high temperatures,other build materials may be used in additive-manufacturing processes asknown in the art to form the first intermediate article from which thecomponent is manufactured.

Upon completion of a respective deposit layer, the fabrication support414 is lowered and the delivery support 434 is raised. The roller orwiper 436 again pushes a portion of the build material 470 from thedelivery device 430 to form an additional deposit layer of buildmaterial 470 on the working plane 416 of the fabrication device 410. Thelaser beam 462 is again controlled to selectively form anothercross-sectional deposit layer of the first intermediate turbine article500. This process is continued as successive cross-sectional depositlayers are built into the first intermediate turbine article 500. Whenthe laser sintering process is completed, the unsintered build material470 is removed and the first intermediate article 500 is removed fromthe fabrication device 410 in anticipation of the subsequent stepsdiscussed below. Although the DMLS process is described herein, othersuitable additive manufacturing processes may be employed to fabricatethe first intermediate article 500.

Post-laser fusion processing may be performed on the first intermediatearticle 500 formed by the additive-manufacturing technique. Suchpost-laser fusion processing may include, for example, stress reliefheat treatments, peening, polishing, hot isostatic pressing (HIP), orcoatings. In some embodiments, one or more of the post-laser fusionprocessing steps discussed below are not necessary and may be omitted.

FIG. 5 shows an exemplary first intermediate article 500 (a firstintermediate turbine article) formed by an additive manufacturingprocess, such as the DMLS process described above. According to anexemplary embodiment, a turbine component will be formed from the firstintermediate turbine article (also identified with reference numeral“500” for ease of illustration). The first intermediate turbine article500 includes internal passages 502 such as internal cooling passagessuch as those in cooled high effectiveness advanced turbine (HEAT) bladeand nozzle parts. Such turbine components may be capable of withstandinghigher temperatures and stresses, thereby leading to furtherimprovements in engine performance. The cooling passages deliver acooling flow to the finished turbine component via an inlet (not shown)during engine operation. The cooling flow exits out various coolingholes (not shown) and out the trailing edge exit slot 504. The coolingpassages may be relatively complex and intricate for tailoring the useof the limited pressurized cooling air and maximizing the coolingeffectiveness thereof and the overall engine efficiency. The internalsurfaces 304 a of the internal passages 502 (“internal passagesurfaces”) illustrated in FIG. 5 are rough, being uneven and irregular,such surface roughness indicated with reference character 505. Surfaceroughness may be caused by contamination, debris, oxidation, or thelike. Random near-surface particles (i.e., debris) are identified inFIG. 6 with reference character 507. While not shown, the externalsurface 304 b of the first intermediate article 500 may also exhibitsurface roughness.

As a result of the additive manufacturing process, the firstintermediate article 500 may include internal passage surface roughness,external surface roughness (external surface roughness not shown in FIG.5), or both. The first intermediate article 500 may also include surfaceconnected porosity and cracks 506 and internal porosity and cracks 508within the material substrate 510, as well as interface defects (notshown in FIG. 5) and may not be suitable for use without furtherprocessing to reduce or substantially eliminate such defects. The term“porosity” used herein refers to a defect that comprises small spaces orvoids within the material substrate 510. The term “cracks” used hereinrefers to linear defects or voids within the material substrate 510, andincludes microcracks. As noted above, the term “surface-connecteddefects” includes defects (porosity and cracks) at the surface, nearsurface and subsurface with the cracks having faying surfaces, as notedabove.

FIG. 6 illustrates a portion of the first intermediate article of FIG.5, including a portion of the material substrate 510 and arepresentative rough internal passage surface thereof. The materialsubstrate 510 also includes an exemplary internal defect 508. As notedabove, for components with high surface roughness, the structuralintegrity and mechanical properties thereof may be compromised. Inaddition, for those components with high surface roughness also needinga reduction in internal and surface-connected defects, surface-connecteddefects thereof may not be successfully bridged and covered by anencapsulation layer to convert the surface-connected defects intointernal defects in preparation for subsequent HIP processing. As notedabove, HIP processing reduces or substantially eliminates internaldefects.

FIGS. 7 through 9 are successive cross-sectional views of the method 10for manufacturing a component, according to exemplary embodiments. Themethod 10 may be used to reduce surface roughness on first intermediatearticles formed by additive manufacturing processes to improve thestructural integrity and mechanical properties of the component. Themethod 10 may also or alternatively be used to improve metallurgicalsurface integrity of the component.

Referring again to FIGS. 3 and 7, in accordance with exemplaryembodiments, method 10 continues by applying a layer 302 of coatingmaterial (hereinafter “a coating material layer”) on the firstintermediate article (step 320). The coating material layer may be, forexample, an aluminum-containing coating material layer. The as-appliedlayer 302 of coating material is ideally metallic and capable ofsubsequent diffusion into a material substrate 510 of the firstintermediate article to form a diffusion coating on the firstintermediate article. As illustrated, the coating material may beapplied to an internal surface 304 a of the first intermediate articleto ensure that the coating material layer 302 spans thesurface-connected porosity and cracks 506 within, for example, theinternal passages 502 (FIG. 5). The coating material may be applied byany known coating techniques such as, for example, chemical vapordeposition, plating, or the like. The coating material is alsopreferably sufficiently ductile such that it conforms or deforms to thecontour of the first intermediate article prior to (during the applyingstep) and during heating for a hot isostatic pressing (HIP) process step384, as hereinafter described.

Still referring to FIG. 3 and now to FIG. 8, in accordance withexemplary embodiments, method 10 continues by thereafter diffusion heattreating the first intermediate article 500 and the coating materiallayer 302 to form the diffusion coating 306 on the first intermediatearticle (step 340). The diffusion coating 306 comprises a surfaceadditive layer 310 and a diffusion zone or layer 312 below the surfaceadditive layer 310. The surface additive layer 310 is the coatingmaterial layer 302 depleted in one or more elements after diffusing intothe parent metal of the material substrate 510. Note that in FIG. 8, therandom near-surface particles 507 are also part of the diffusion layer312, which is why they can be subsequently removed as hereinafterdescribed.

Diffusion heat treating may be performed at elevated temperatures ofbetween about 871° C. to about 1093° C. (1600-2000° F.) for about twohours to about twenty hours. In other embodiments, the diffusion heattreatment may occur at a temperature and/or for a time period (duration)outside of the aforementioned ranges. After diffusion heat treating, thesecond intermediate article may be cooled.

During the applying step 320, if performed at a sufficiently elevatedtemperature, a primary diffusion zone occurs to some degree between thecoating material layer 302 and the substrate 510 as a result of theconcentration gradients of the constituents. At elevated temperatures ofthe diffusion heat treating step 340, further interdiffusion occurs as aresult of solid-state diffusion across a coating bond line 311 (FIG. 8).The coating bond line 311 is the demarcation between the applied coatingmaterial layer and the substrate 510 of the first intermediate article.The coating bond line 311 is the “edge” of the first intermediatearticle. When the applied coating material layer is used as an oxidationprotective coating, it is important that there be a good bond with thesubstrate of the first intermediate article at the coating bond line 311to prevent spalling of the applied coating material layer. Theadditional migration of elements across the coating bond line 311 in thediffusion heat treating step 340 can sufficiently alter the chemicalcomposition and microstructure of both the diffusion layer 312 and thesubstrate 510 in the vicinity of a coating diffusion boundary 314. Thediffusion zone or layer 312 includes an upper portion of the substratein the vicinity of the coating bond line 311. The coating diffusionboundary 314 separates the diffusion layer 312 from the materialsubstrate 510 below the coating diffusion boundary 314. As illustratedin FIG. 8, the coating diffusion boundary 314 is relatively smoothcompared to the original rough surface 304 a of the material substrate510 as illustrated in FIGS. 5 and 6. The coating diffusion boundaryshould be sufficiently sharp or defined such that removal of thediffusion coating yields a material substrate 510 having a surfacecomposition very close to that of the parent metal before diffusion. Theactivity of the diffusion process influences the structure of thediffusion coating formed. “Low activity” processes produce “outwardly”diffused coatings where the diffusion coating forms predominately by theoutward migration of elements from the substrate and its subsequentreaction with the coating material layer at the surface of thesubstrate. “High activity” processes produce “inwardly” diffusedcoatings where the diffusion coating forms predominately by migration ofthe elements in the coating material layer into the surface of thesubstrate.

A thickness of the diffusion layer 312 of about 0.2 to about 3 mils isoptimal, and corresponds to how much of the upper portion of thesubstrate of the first intermediate article will be removed in step 360.Internal passage surface diffusion layers are typically much thinnerthan diffusion layers on external surfaces and steps can be taken toselectively reduce the thickness of the diffusion layer on the externalsurfaces to arrive at a more even diffusion coating overall to betterhold dimensions following removal of the diffusion coating, ashereinafter described. If significant surface roughness andsurface-connected defects exist, a thicker diffusion coating may benecessary. The surface additive layer has to be sufficiently thick andcontinuous to serve as the reservoir for the diffusing element (e.g.,aluminum) to diffuse into the substrate, either during step 340 orduring step 384.

In accordance with an exemplary embodiment, the diffusion coating may bean aluminide diffusion coating formed by a high activity diffusioncoating process. Any aluminizing technique for forming the aluminidediffusion coating is acceptable, for example, a liquid phase slurryaluminizing process, a pack cementation process, a chemical vapor phasealuminizing process, or the like as known in the art. As used herein, an“aluminizing” step comprises applying an aluminum-containing oraluminum-rich coating material layer and diffusion heat treatmentthereof. The aluminum may be applied using a single deposition processor a combination of processes. For example, formation of the aluminidediffusion coating may be accomplished in an exemplary slurry aluminizingprocess by heating a slurry coated first intermediate article in anon-reactive environment to a diffusion temperature between about 871°C. to about 1093° C. (1600-2000° F.) for about two to about twentyhours. Suitable non-reactive environments in which the diffusion may beperformed include vacuums and inert or reducing atmospheres. Dry argon,hydrogen, dissociated ammonia or mixtures of argon and hydrogen arerepresentative types of gases suitable for use as non-reactiveenvironments. The heating melts the aluminum powder in the slurry andpermits the reaction and diffusion of the aluminum into the substratesurface. It has been found that when a slurry coated first intermediatearticle is heated to temperatures of about 980° C. (1800° F.), thealuminum powder melts and diffuses into the substrate to produce thealuminide diffusion coating, that is, NiAl on a nickel alloy and CoAl ona cobalt alloy, thereby aluminizing the superalloy substrate.

Still referring to FIG. 3 and to FIGS. 9-10, according to exemplaryembodiments, method 10 continues by removing the diffusion coating 306(step 360) (also referred to herein as “stripping”) to form a secondintermediate article 600 (FIG. 10) having at least one enhanced surface318. The exemplary second intermediate article 600 illustrated in FIG.10 is a second intermediate turbine article. The layers 310 and 312 ofthe diffusion coating 306 are substantially removed in their entirety tothe coating diffusion boundary 314 thereby forming the at least oneenhanced surface 318. In accordance with exemplary embodiments, removalof the diffusion coating 306 removes both the surface additive layer 310and the diffusion layer 312 under the surface additive layer, includingthe random near-surface particles 507. As the diffusion layer 312includes the upper portion of the substrate (the portion of thesubstrate in the vicinity of the coating bond line 311), the upperportion of the substrate will also be removed. The coating diffusionboundary 314 thus becomes the at least one enhanced surface 318 of thesecond intermediate article. The diffusion coating and removal stepsfunction to reduce surface roughness, resulting in the secondintermediate article having the at least one enhanced surface. Thecoating diffusion boundary should be sufficiently defined or sharp suchthat removal of the diffusion coating yields a substrate surfacecomposition very close to that of the original substrate.

The diffusion coating 306 may be removed by any known diffusion coatingremoval technique. For example, the cooled component may be flushedinside and out in a chemical solvent such as ferric chloride, nitricacid, etc. The chemical solvent is selected for its ability to removethe diffusion coating, without affecting the integrity of the substrate.The coating removal chemical compositions and concentrations may bemodified to optimize the amount of diffusion coating removed and/or theremoval time while maintaining the integrity of the substrate. Thedimensions of the original model for the component may be modified toaccommodate removal of the upper portion of the original substrate abovethe coating diffusion boundary to allow the finished component to meetfinished component dimensions.

While reduction of internal passage surface roughness has been describedand illustrated, it is to be understood that external surface roughnessmay be reduced in the same manner. Thus, the coating material layer maybe applied on at least one surface of the first intermediate article,the at least one surface being an internal passage surface, an externalsurface, or both the internal passage surface and the external surface.The at least one enhanced surface may therefore be an enhanced internalpassage surface, an enhanced external surface, or both. The externalsurface of the first intermediate article may not need to be “enhanced”by formation and removal of the diffusion coating (steps 320, 340, and360), as conventional polishing or mechanical finishing (using abrasivesanding belts, for example) may be more practical to reduce externalsurface roughness. However, certain component geometries make mechanicalfinishing costly or impractical. For example, for the turbine articleshown in the image of FIG. 15, polishing or mechanical finishing of theexternal surface was practical, but for other more complex externalgeometries, it may be better to use steps 320, 340, and 360 to enhancethe external surface. Conventional polishing and formation and removalof the diffusion coating may also be performed, according to exemplaryembodiments. The internal passage surface roughness may be reducedbefore, concurrently, or after external surface roughness is reduced.

If there is residual surface roughness or surfaces with inadequatediffusion bonded faying surfaces (“diffusion bonding failures”), formingof the diffusion coating (applying and diffusion heat treating steps)and removal thereof (hereinafter collectively a “forming and removingcycle”) may optionally be repeated as many times as necessary until theat least one surface of the article is sufficiently enhanced, thesufficiency thereof known to one skilled in the art. As noted above, theterm “enhanced” or the like refers to a reduction in surface roughnessand/or improvement in metallurgical quality. The improvement inmetallurgical quality results from removing surfaces lacking sufficientmetallurgical surface integrity caused by inadequately metallurgicallydiffusion bonded faying surfaces of the surface-connected cracks. Forexample, referring to FIGS. 8 and 9, while surface roughness has beenreduced by at least one forming and removing cycle, residualsurface-connected cracks 509 having inadequately diffusion bonded fayingsurfaces 511 are still present, extending deeper into the surface of thematerial substrate 510 below the coating diffusion boundary 314. Thus,additional forming and removing cycles are needed to remove the affectedsurface(s) to improve the metallurgical quality of the component.

For some components exposed to low operating stresses, it may besufficient to reduce surface roughness by performing steps 320, 340, and360 at least once without further processing. That is, if the surfacefinish is sufficient, the process is finished. If the surface finish isinsufficient, steps 320, 340, and 360 may be repeated. However, forother environments, concerns about surface-connected defects andinternal defects may be relevant. In accordance with exemplaryembodiments, as illustrated in FIG. 3, surface roughness may be reducedconcurrently with converting surface-connected defects in the firstintermediate article into internal defects and/or concurrently withreducing or eliminating internal defects therein. In an embodiment, thecoating material layer 302 applied in step 320 and diffused in step 340to form the surface additive layer and the diffusion layer of thediffusion coating may also serve as an encapsulation layer. Anencapsulation layer functions to effectively convert thesurface-connected defects 506 into internal defects 508. In this case,as hereinafter described, no subsequent encapsulation 382 in a finishingstep 380 as hereinafter described may be necessary.

To reduce or eliminate internal defects in the first intermediatearticle, a hot isostatic pressing (HIP) process or other consolidationprocess may be performed concurrently with the diffusion heat treatingstep 340, as the heating during the HIP process results in bothinterdiffusing the substrate and the coating material layer to form thediffusion coating and consolidation of the first intermediate article toreduce or substantially eliminate internal defects. In this case, nosubsequent consolidation or HIP processing 384 in the finishing step 380may be necessary. Thus, if the only issue is surface roughness and/ordiffusion bonding failures, or if the surface roughness is reducedconcurrently with converting surface-connected defects and reducing oreliminating internal defects, the method does not proceed to steps 380,382, and/or 384 as shown by the dotted lines in FIG. 3.

In the hot isostatic pressing (HIP) process, the article is subjected toelevated temperatures and pressures over time. In general, the HIPprocess will not reduce defects such as porosity or cracks that areconnected to the surface of the component. As noted above, HIPprocessing reduces or substantially eliminates internal defects. The HIPprocess may be performed at any temperature, pressure, and time that aresuitable for forming a compacted solid having minor or acceptable levelsof porosity. For example, the HIP process may be performed at aprocessing temperature in a range of about 1000° C. to about 1300° C.and may be performed at a pressure in a range of about 1 ksi to about 25ksi for a time period of about 1 to about 10 hours. In otherembodiments, the HIP processing temperature, pressure, and time may behigher or lower to form a compacted article having negligible cracks andporosity. The consolidated article may comprise the finished component.

While the HIP process on the first intermediate article is described andillustrated as being performed after encapsulation, it is to beunderstood that the HIP process on the first intermediate article may beperformed without prior encapsulation. It is also to be understood thatthe HIP process may be performed anytime, in order to reduce orsubstantially eliminate internal defects.

In other embodiments, converting the surface-connected defects intointernal defects in preparation for HIP processing and/or HIP processingof the second intermediate article 600 may occur after the surfaceroughness has been reduced. Referring again to FIG. 3 and to FIGS.11-13, in accordance with an exemplary embodiment, method 10 continuesby optionally finishing the second intermediate article 600 (FIG. 10)(the second intermediate turbine article) to produce the finishedcomponent 900 (step 380). The encapsulation and consolidation by a HIPprocess during finishing step 380 is used when a decision is made to usea non-diffusion coating on an improved surface article. That might bethe case where the first HIP process (e.g., in step 340) isintentionally or unintentionally limited in its effectiveness toconsolidate and heal internal defects. Also, should the thickness of thearticle be too thin, one might not want to risk further thinning aswould happen if a diffusion coating was applied. Thus, step 380 offersan encapsulation process for HIP with a minimal loss of thickness. Step380 does not exclude repeating steps 320, 340, and 360 if necessary tofurther improve the metallurgical surface quality of the article. Theexemplary finished component illustrated in FIG. 13 is a finishedturbine component in which internal passage surface roughness has beenreduced, and the surface-connected defects and internal defects havebeen reduced or substantially eliminated (no interface defects shown inFIGS. 5-11). In some exemplary embodiments as noted above, no suchfinishing treatments are necessary and step 380 may be omitted. In step380, the second intermediate article 600 may undergo further processingincluding finishing treatments. Such treatments may include, forexample, aging, solutioning, annealing, quenching, peening, polishing,hot isostatic pressing (HIP), or coatings, such as bond coatings,thermal barrier coatings, or the like. Although step 380 is referred toas a finishing treatment, such treatments may be used at other times, ashereinafter described. As one example, surface peening or polishing ofthe external surface may be provided before, during, or after reducingthe surface roughness of the internal passage surface(s).

Examples of a finishing treatment of step 380 are discussed below withreference to FIGS. 11 and 12. FIGS. 11 and 12 are successivecross-sectional views of the step 380 applied to the second intermediateturbine article 600 (FIG. 10) after removal of the diffusion coating 306in step 360. Referring now to FIG. 11, the second intermediate turbinearticle of FIG. 10 is shown encapsulated with an encapsulation layer 602forming an encapsulated article 700. Encapsulation layer 602 refers toan encapsulation layer formed during the finishing step 380. Theencapsulation layer 602 also functions to effectively convert thesurface porosity and cracks 506 into internal porosity and cracks 508.For example, the surface porosity and cracks 506 of FIG. 5 areeffectively internal porosity and cracks 508 in FIG. 11 as a result ofthe encapsulation layer 602. Any suitable encapsulation process may beperformed that bridges and covers the porosity and cracks in the atleast one surface of the article. For example, the encapsulation layer602 may have a thickness of approximately 10-100 um, although anysuitable thickness may be provided. Such encapsulation layer may besubsequently removed (See FIG. 13) or maintained to function as anoxidation protection layer. The encapsulation layer may be a metal oralloy that is compatible with the substrate material and may be formed,for example, by a plating process or a coating process, as hereinafterdescribed. In various exemplary embodiments, the encapsulation layer 602of finishing step 380 may be formed for example, by electroless platingor electroplating processes. In further embodiments, the encapsulationlayer may be formed by processes including cobalt plating, sol-gelchemical deposition techniques, or low pressure plasma sprays. Asuitable material for the encapsulation layer is one which when appliedor when heated to the HIP temperature is relatively ductile and free ofgaps or cracks and which spans the surface-connected porosity and cracks506 within, for example, the internal passages 502. As noted above,other examples of suitable encapsulation layers 602 include an aluminidediffusion coating or other diffusion coating.

Referring now to FIG. 12, another exemplary finishing treatment of step380 includes consolidating the second intermediate article and theencapsulation layer by, for example, the hot isostatic pressing (HIP)process (step 384) in which the article is subjected to elevatedtemperatures and pressures over time to form a consolidated article 800.The encapsulation layer 602 provided in FIG. 11 (or the encapsulationlayer provided by steps 320 and 340) functions to internalize any suchsurface connected defects (e.g., surface connected porosity and cracks)such that the HIP process is effective for all or substantially all ofthe internal cracks or porosity in the material substrate 510, includingcracks and porosity that would otherwise be surface porosity and cracks506 as illustrated in FIG. 10. The consolidated article may comprise thefinished component. While the HIP process of the finishing step 380 isalso described and illustrated as being performed after encapsulation,it is to be understood that the HIP process 384 may be performed withoutprior encapsulation. Again, it is to be understood that the HIP processmay be performed anytime, in order to reduce or substantially eliminateinternal defects.

While the method illustrated in FIG. 3 involves four decision questions,it should be understood that not all the decision questions necessarilyapply in the manufacture of a particular component. For example, if onlysurface roughness or diffusion bonding failure is of concern, the methodmay stop after steps 320, 340, and 360 have been performed at least onetime. If internal defects are the only concern, consolidation (step 384)only may be performed.

Returning again to FIG. 3, upon completion of step 360 or step 380, thecomponent produced in accordance with exemplary embodiments, may bemachined to the final specifications. The machining techniques for aturbine component may include, for example, the addition of a tip cap,formation of cooling holes, and grinding the rotor tips as known in theart. At this point, the turbine component 900 in FIG. 13 corresponds tothe completed turbine component 200 shown in FIG. 2. The completedcomponent may be positioned for its intended use. For example, acompleted turbine component may be installed in a turbine section of thegas turbine engine as shown in FIG. 1.

EXAMPLE

The following example is provided for illustration purposes only, and isnot meant to limit the various embodiments of the present invention inany way. In the following example, an aluminide diffusion coating isformed on an internal surface of an exemplary turbine article (an HPturbine blade) formed from a DMLS additive manufacturing process usinghigh temperature, high strength nickel-based superalloys (MM247 andIN738), in accordance with exemplary embodiments. FIGS. 14-17 are imagesof the exemplary turbine article or portions thereof. As shown in FIG.14, the turbine article has both internal passage surface roughness anddefects (the internal surface referred to by reference element 304 a)and external surface (304 b) roughness and defects. FIG. 15 is an imageof the turbine article of FIG. 14 after encapsulation and HIPprocessing. The external surface 304 b was conventionally polished priorto encapsulation and HIP processing to eliminate the external surfaceroughness and defects. However, the internal passage surface of theturbine article of FIG. 15 still has significant surface roughness andsurface-connected defects, even after encapsulation and HIP processing,as shown more clearly in the image of FIG. 16. FIG. 17 is an image of aportion of the turbine article after forming an aluminide diffusioncoating on the internal surface, illustrating a relatively smoothcoating diffusion boundary 314. The aluminide diffusion coating of FIG.17 was prepared according to the steps described above using a chemicalvapor deposition aluminizing process performed at between 1950° F. to2000° F. for two to four hours. The aluminide diffusion coating of FIG.17 was formed according to steps 320 and 340 (FIG. 3) and pictoriallyillustrated in FIGS. 7 and 8. The aluminide diffusion coating formed asharp (i.e., clearly defined) coating diffusion boundary 314. While notshown in the images, the aluminide diffusion coating will besubsequently removed to the coating diffusion boundary 314 forming thesecond intermediate turbine article 600 (FIG. 10) having at least oneenhanced surface 318. The enhanced surface 318 of the secondintermediate article will have a surface composition very close to thatof the material substrate 510. The second intermediate article maycomprise the turbine component or be finished or completed as describedabove.

Accordingly, methods in accordance with exemplary embodiments may reducesurface roughness and/or improve metallurgical quality of articlesformed by additive manufacturing processes. These methods yieldcomponents with improved overall structural integrity, cosmeticappearance, functionality, mechanical properties, and fatiguelife/strength. Exemplary embodiments also reduce or substantiallyeliminate surface-connected and internal defects of the articles. Thesemethods also improve yield and enable improved development cycle timesand reduced tooling costs associated with component manufacturingwithout sacrificing component performance or durability. Additionally,these methods permit internal configurations for components nototherwise possible with conventional fabrication technologies, withoutelaborate tooling.

While at least one exemplary embodiment has been presented in theforegoing detailed description of the invention, it should beappreciated that a vast number of variations exist. It should also beappreciated that the exemplary embodiment or exemplary embodiments areonly examples, and are not intended to limit the scope, applicability,or configuration of the invention in any way. Rather, the foregoingdetailed description will provide those skilled in the art with aconvenient road map for implementing an exemplary embodiment of theinvention. It being understood that various changes may be made in thefunction and arrangement of elements described in an exemplaryembodiment without departing from the scope of the invention as setforth in the appended claims.

What is claimed is:
 1. A method for manufacturing a component, themethod comprising the steps of: forming a diffusion coating on a firstintermediate article formed by an additive manufacturing process, thediffusion coating comprising a surface additive layer and a diffusionlayer below the surface additive layer, the diffusion layer including anupper portion of a material substrate of the first intermediate article;and removing the diffusion coating from the first intermediate articleforming a second intermediate article, the step of removing thediffusion coating includes removing the upper portion of the materialsubstrate to a coating diffusion boundary, wherein the forming andremoving steps comprise a forming and removing cycle that is repeated atleast once during manufacture of the component.
 2. The method of claim1, wherein the step of forming a diffusion coating comprises: applying alayer of coating material on a surface of the first intermediatearticle; diffusion heat treating the first intermediate article and thelayer.
 3. The method of claim 1, wherein the step of forming a diffusioncoating on a first intermediate article comprising forming the diffusioncoating on the first intermediate article formed from a build materialcomprising an alloy, a superalloy, titanium, chromium, stainless steels,and combinations thereof.
 4. The method of claim 2, wherein the step ofapplying a layer of coating material comprises applying the layer ofcoating material comprising a metallic material comprising one or moremetallic elements.
 5. The method of claim 2, wherein the step ofapplying a layer of coating material comprises applying the layer ofcoating material layer to conform or deform to the contours of the firstintermediate article.
 6. The method of claim 2, wherein applying thelayer of coating material on the surface comprises applying the layer ofcoating material on an internal passage surface, an external surface, orboth the internal passage surface and the external surface of the firstintermediate article.
 7. The method of claim 2, further comprising thestep of consolidating the first intermediate article by a hot isostaticpressing (HIP) process concurrently with the step of diffusion heattreating.
 8. The method of claim 2, wherein the step of forming adiffusion coating on a first intermediate article provides anencapsulation layer on the first intermediate article, the encapsulationlayer comprising the surface additive layer, the diffusion layer, orboth the surface additive layer and the diffusion layer.
 9. The methodof claim 8, further comprising the step of consolidating the firstintermediate article by a hot isostatic pressing (HIP) processconcurrently with the step of diffusion heat treating or consolidatingthe second intermediate article by the hot isostatic pressing (HIP)process.
 10. The method of claim 1, further comprising the step ofconsolidating the second intermediate article by a hot isostaticpressing (HIP) process.
 11. The method of claim 10, further comprisingthe steps of: encapsulating the second intermediate article with anencapsulation layer to form an encapsulated article prior to the step ofconsolidating the second intermediate article; and optionally removingthe encapsulation layer after the consolidating step.
 12. The method ofclaim 1, wherein the step of removing the diffusion coating removes theupper portion of the material substrate to the coating diffusionboundary defining an enhanced surface of the second intermediatearticle.
 13. A method for manufacturing a component from a firstintermediate article formed by an additive manufacturing process, themethod comprising: applying a coating material layer on a surface of thefirst intermediate article; diffusion heat treating the firstintermediate article and the coating material layer to form a diffusioncoating on the first intermediate article, the diffusion coatingcomprising a surface additive layer and a diffusion layer below thesurface additive layer, the diffusion layer including an upper portionof a substrate of the first intermediate article; removing the diffusioncoating including the upper portion of the substrate from the firstintermediate article forming a second intermediate article; and if thereis residual surface roughness or diffusion bonding failures remainingafter the removing step, repeating the applying, diffusion heattreating, and removing steps at least once, the steps of applying,diffusion heat treating, and removing comprising a forming and removingcycle that is repeated at least once during manufacture of the componentfrom the first intermediate article.
 14. The method of claim 13, whereinthe substrate comprises a superalloy, an alloy, titanium, chromium,stainless steels, or combinations thereof and the coating material layeris metallic comprising one or more metallic elements.
 15. The method ofclaim 13, wherein the step of applying a coating material layer on asurface of the first intermediate article comprises applying the coatingmaterial layer on an internal passage surface, an external surface, oron both the internal passage surface and the external surface.
 16. Themethod of claim 13, further comprising the step of consolidating thefirst intermediate article by a hot isostatic pressing (HIP) processconcurrently with the step of diffusion heat treating.
 17. The method ofclaim 13, wherein the steps of applying and diffusion heat treatingprovide an encapsulation layer on the first intermediate article, theencapsulation layer comprising the surface additive layer, the diffusionlayer, or both the surface additive layer and the diffusion layer, themethod further comprising the step of consolidating the firstintermediate article by a hot isostatic pressing (HIP) processconcurrently with the step of diffusion heat treating or the secondintermediate article by the hot isostatic pressing (HIP) process. 18.The method of claim 13, further comprising the step of consolidating thesecond intermediate article by a hot isostatic pressing (HIP) process.19. The method of claim 18, further comprising the steps of:encapsulating the second intermediate article with an encapsulationlayer to form an encapsulated article prior to the step of consolidatingthe second intermediate article; and optionally removing theencapsulation layer after the consolidating step.